The invention relates to a novel silicone-based material. It applies more particularly, but without limitation, to a novel material for dental impression.
It also relates to a method of producing this material.
Many materials are currently used for the production of dental impressions and more particularly materials based on silicone or alginate.
The invention relates particularly to silicone-based materials. In a known manner, silicones are obtained by the crosslinking of a xe2x80x9cbasexe2x80x9d of the organochlorosilane type, the crosslinking being initiated by a catalyst. The silicones obtained are either polycondensed silicones or silicones resulting from a polyaddition reaction.
In practice, silicones exist in the form of a thick or fluid paste which is placed on the base of a metal impression tray whose shape adopts that of the dental arch.
The impression tray/material assembly is then placed in the mouth and manually applied onto the dental arch for a period of between one and four minutes, according to the structural characteristics of the material used.
The impression tray and the material are then removed from the mouth and then sent to the dental technician who will produce the final prosthesis.
Even if the period during which the impression material remains in the mouth is relatively short, it is nevertheless sufficient for the material to be covered with the saliva and blood present in the patient""s mouth. A number of bacteria, microbes and the like are then likely to develop not only at the surface, but also in the impression, which requires disinfecting the material as soon as it is removed from the patient""s mouth, this being in order to observe basic rules of hygiene not only in relation to the dentist but also in relation to the dental technician. In addition, the patient is also concerned since it appears that often the prosthesis travels between the dental technician and the dentist in the same box as that in which the original impression tray existed.
As a method of disinfection, it is proposed in the document U.S. Pat. No. 5,624,636 to soak the dental impression in a hypochlorite bath for a period of between 1 and 5 minutes. A very relative efficacy of this type of treatment is observed since only a surface treatment is obtained.
To disinfect not only the surface but also the mass of the impression, it has been proposed in the document EP-A-0,361,301 to incorporate instead of the water necessary for the preparation of an alginate impression, an aqueous and microbicidal solution containing quaternary ammonium salts and a diguanidine compound, of specific formulae.
Even if this antiseptic is effective, it can only be introduced into a hydrophilic impression material, such as alginate, but is not in any case compatible with a hydrophobic material such as silicone. In addition, size stability problems are encountered as well as chemical and physical stability problems.
In other words, none of the solutions proposed up until now makes it possible to effectively disinfect the surface and the inside of a silicone-based impression since the treatment by the external route remains only slightly effective and the treatment by the internal route is effected using hydrophilic antiseptic agents, which cannot therefore be incorporated into hydrophobic materials.
The problem which the invention proposes to solve is therefore to provide a silicone-based dental impression material which is capable of being effectively disinfected.
To do this, the invention provides a silicone-based dental impression material comprising a hydrophobic antiseptic agent incorporated into the mass of the silicone and which can be gradually released up to the surface of the impression.
In other words, the invention consists in having incorporated an antiseptic agent which is compatible with silicone, and therefore hydrophobic, and which has the capacity to be released over time, developing a specific action, namely the gradual ionic release, allowing the disinfection both of the mass and the surface of the impression. The antiseptic agent therefore acts by an innovative process of self-disinfection of the silicone.
According to a first characteristic of the invention, the antiseptic agent comprises a chelating agent, an agent which is active on the phospholipid membranes of bacteria or viruses, and an agent which is active on the nucleocapsids of viruses or on any bacteria receptor site.
As chelating agent, ethylenediaminetetraacetic acid is advantageously used.
Moreover, the agent which is active on the phospholipid membranes of bacteria or viruses is a quaternary ammonium salt, in particular benzalkonium chloride.
As regards the agent which is active on the nucleocapsids of viruses or on any bacteria receptor site, sodium tosylchloramide or one of its chlorinated analogs is preferably used.
In other words, the antiseptic agent acts within the mass of the impression, gradually releasing the active chlorine ions derived from the benzalkonium chloride and those derived from the sodium tosylchloramide up to the surface of the impression. Thus by virtue of the internal and external action of the antiseptic agent, an impression free of any infectious microbes, viruses or bacteria is obtained in particular by virtue of the attachment of the chlorine atoms to the bacteria and virus receptor sites.
According to a preferred embodiment, the antiseptic agent comprises by mass:
between 8 and 80% of ethylenediamine-tetraacetic acid;
between 2 and 20% of benzalkonium chloride;
between 1 and 20% of sodium tosylchloramide or one of its chlorinated analogs.
To promote galenic homogenization of the antiseptic preparation, the latter comprises a double amino acid, in particular aspartame.
To obtain an additional antiinflammatory and cicatrizing effect, the antiseptic agent comprises allantoin.
As sweetener and isotonicity adjuvant, the antiseptic agent comprises a natural flavoring and sorbitol.
To obtain a material free of any bacteria, microbes, viruses and the like, the proportion of antiseptic agent in said material is between 0.1 and 1% by mass.
For a value less than 0.1%, the proportion of antiseptic agent is not sufficient to obtain a disinfecting effect.
Likewise, a proportion of antiseptic agent greater than 1% does not improve the result obtained.
The invention also relates to the method of producing a silicone-based dental impression material, said silicone being obtained by the crosslinking of an organochlorosilane base, said crosslinking being initiated by a catalyst.
This method is characterized in that the antiseptic agent described above is incorporated into the organochlorosilane base, and then said organochlorosilane base is mixed with the catalyst in order to obtain the final material after crosslinking.
According to an essential characteristic of the method, the antiseptic agent comprises by mass:
from 8 to 80% of diethylenediaminetetraacetic acid;
from 2 to 10% of benzalkonium chloride;
from 1 to 10% of sodium tosylchloramide or one of its chlorinated analogs.
According to a preferred embodiment of the method, before incorporating the antiseptic agent into the organochlorosilane base:
the antiseptic agent is mixed beforehand with a silicone oil,
the mixture obtained is then stirred and it is allowed to separate by settling,
and finally, after filtration, the dispersion obtained is incorporated into the organochlorosilane base.